You have to ask how social interaction could increase survival rate. Take one example: If a group of 20 co-ordinates in a hunting party to fell a large beast,

You have to ask how social interaction could increase survival rate. Take one example: If a group of 20 co-ordinates in a hunting party to fell a large beast, the payoff (i.e., the meat) benefits a much larger group. That increased caloric intake directly affects survival. Mutations that aided social skills would benefit the organ producing those "tools". And on and on for generations...